a) Field of the Invention
The invention is directed to a process for generating a stereoscopic video picture by means of partial images for the left eye and for the right eye of an observer, these partial images emitting light with different polarization states oriented orthogonally relative to one another, wherein the observer perceives the stereoscopic video picture through spectacles with eyepieces which filter the respective polarization state of the light. The invention is further directed to a device for generating a stereoscopic video picture by means of partial images for the left eye and for the right eye of an observer, these partial images emitting light with different polarization states oriented orthogonally relative to one another, wherein the observer perceives the stereoscopic video picture through spectacles with two eyepieces which filter the respective polarization state of the light.
b) Description of the Related Art
The representation of three-dimensional images is desired for the future development of video technology not only because of increased entertainment value in television, but also because three-dimensional pictures can be used as design aids in computer aided design, since the designed element can be observed directly and two-dimensional views with auxiliary lines for hidden edges are dispensed with.
There are essentially two methods to be distinguished in the known prior art for representing three-dimensional video pictures. In the first method, the three-dimensional pictures are imaged as plane sectional images in a plurality of planes arranged one behind the other. The second method makes use of the fact that an observer only recognizes a three-dimensional picture in that he observes an object through both eyes from different viewing angles. By using this second method (stereoscopy, as it is called), two pictures detected from different viewing angles are presented to the left eye or right eye so that the object shown on the pictures is perceived three-dimensionally by the observer's brain as is customary in normal vision. The stereoscopic process uses special spectacles which filter the two pictures out of an overall picture and present these pictures to the left eye or right eye of the observer.
The imaging of three-dimensional pictures in a plurality of picture planes in accordance with the first method is described in WO 79/00308 A1 and EP 0 311 843 A2. Special spectacles are not used in this type of image generation. However, three-dimensional pictures shown in this way require a substantially greater amount of information than would be required for the transmission of only two pictures separately for the left eye and right eye. Therefore, it is not expected that these devices will be put to general use in video and television technology in the near future.
The second method, that of generating stereoscopic images, is also used in the process and device mentioned in the introduction. Two partial images are generated with different polarization states orthogonal to one another and are superimposed. Spectacles worn by the observer then filter out the partial image for the left eye and the partial image for the right eye via polarizing filters.
Processes and devices of this type are known from DE 39 10 420 A1, EP 0 328 357 A2, DE 36 07 629 C2, DE 32 01 837 A1, and DE 32 14 327 A1. In order to represent two pictures, one for each eye of the observer, picture tubes are used as is conventional in television technology. By means of polarizing filters located in front of a picture tube, the polarization of the image emanating from the light, depending upon the partial image represented, is either changed alternately or partial images generated on two picture tubes are projected upon one another after filtering the picture with different polarization. The observer wears spectacles with two polarizing filters filtering out different polarization states; the polarizing filters allow one of the partial images to pass through for each eye. If two partial images are taken by different cameras spaced apart at a defined distance, for example, this results in a stereoscopic image for the observer.
However, using polarizing filters in the spectacles and acting upon the superposed partial images with additional polarization leads to energy losses which must be taken into account in generating pictures. In very large-picture screen surfaces, the increased energy necessitated by this loss can result in heat problems requiring cooling. Thus, the undesirably high energy consumption is compounded by increased constructional expense.
In accordance with DE 31 34 649 A1, DE 32 26 703 A1, EP 0 076 015 A1, EP 0253 121 A2 and WO 80/1447 A1, the two pictures are represented in different colors for the left eye and right eye. Spectacles provide for the selection of the pictures generated for the left eye and right eye by means of color filters. Large energy losses are also inevitable when filtering out colors.
In addition to the large intensity losses caused by color filters, this technique also has the disadvantage that high-quality stereoscopic color pictures are rendered impossible because the color information already in use for allocating the pictures to the respective eyes is thus not fully available for showing colors.
Another device (DE 37 29 521 A1) does not need to use polarized light because the partial images for the left eye and right eye are generated in alternating cycles, wherein the information for the left eye and right eye is screened out synchronously with the presentation of the corresponding partial image with the aid of spectacles. This technique would appear suitable for reducing energy losses compared with the prior art indicated above. However, this assumption has proved wrong in practice. Because of the rapidity of the observer's eye, the switching frequencies for opening and closing the shutters contained in the spectacles must be very high. Moreover, in order to avoid possible disturbing noise which is to be expected in the mechanical execution of this shutter mechanism, only LCD arrays can be used as shutters in practice. However, these LCD arrays also pass only a small portion of the light and thus likewise result in large energy losses.
This technique using spectacles provided with shutters was used in connection with film projection for the Sony Theater in Lincoln Square, New York ("SPIEGEL", no. 48, 1994, page 213). Although this method of cinematic projection uses low-loss 15,000-watt xenon lamps such as those developed by NASA for illuminating nighttime space launches, large individual pictures must be used for projection so that the thermal loading of the film remains within acceptable ranges. The article cited above mentions that rolls of film can only be changed with forklifts. This example is a particularly clear illustration of the large energy requirement especially in stereoscopic large-picture representation in accordance with the present state of the art and the resulting impractical handling.
Further, this technique has the disadvantage that a signal must be fed to the shutter-controlled spectacles in order to open the shutter in front of the respective eye. The only alternative to an unmanageable wiring of the spectacles is a remote control, e.g., via infrared light, which sharply increases the cost per set of spectacles.
Arrangements for generating stereoscopic video pictures in which two pictures are presented directly to both eyes are described in DE 34 21 652 A1, DE 31 34 646 A1, EP 0 282 955 A1, EP 0336 628 A1, EP 0262 955 A1, WO 83/02706 A1, and WO 84/01680 A1. These arrangements either use special spectacles in which two stereoscopic partial images are sent to the eyes via prisms or mirrors or the partial images are generated directly by small monitor tubes in the spectacles for each eye.
DE 31 40 404 A1 discloses a projection and recording apparatus in which two pictures are written on different LCD arrays by an individual laser beam making use of the two polarization states of the laser beam and can be projected in a superimposed manner by light from different light sources. Arranged in the path of the laser beam is a controllable polarizing device which passes the light of one polarizing device or the other, depending upon the picture to be written. Although this reference teaches the recording and/or projection of two pictures, the person skilled in the art will not make use of this teaching to generate stereoscopic video pictures, because at least two light sources must be used to display only one picture and also because a large portion of the energy of the two utilized light sources is converted into heat either at the polarizer or at the LCD arrays.